Female strategies of harassment reduction in southern elephant seals

Abstract

Female southern elephant seals are expected to adopt behaviours that reduce the costs of male harassment. We studied the strategies and tactics of harassment reduction in two populations, at Punta Delgada (Valdés Peninsula, Argentina) and at Sea Lion Island (Falkland Islands) during five breeding seasons in all. Females synchronized their breeding activities to reduce harassment risk, and rarely bred alone to reduce the likelihood of encounters with subadult males. Females showed a clear preference for larger harems, that guaranteed a reduced harassment risk: movements between arrival on land and parturition were mostly from smaller to larger harems, and the likelihood of abandonment was lower for large harems. Females protested against approaching males in the vast majority of interactions, regardless of the social context and the status of the interacting male, but protest varied with female breeding status and male phenotype. Frequency of protest of individual females decreased linearly from the beginning of oestrus to departure to sea. Interactions with mature males were less protested. The frequency of protest linearly decreased with increase in age class, and mating attempts by males of higher status and dominance rank were less often protested. Most of this variation with male phenotype, however, was due to the higher probability of older and more dominant males to interact with oestrus females that had an intrinsicly lower tendency to protest. Protest variation in relation to male phenotype was more parsimoniously explained as a consequence of differential access of males to oestrus females rather than of female selectivity. Protests had a role in disruption of mating attempts, although the phenotype of interactors was more important: adult, large and dominant males disrupted interactions regardless of incitation by female protest.

Sexually Antagonistic Coevolution in a Mating System: Combining Experimental and Comparative Approaches to Address Evolutionary Processes

“…2000) and other animals (e.g., Magurran and Seghers 1994;Byrne and Roberts 2000;Galimberti et al 2000;Shine et al 2000) than was previously thought.…”

“…Thus, this simple conflict between the sexes over mating in Gerris might constrain their key mating behaviors and associated morphologies to a limited number of evolutionary pathways. Similar conflicts over mating appear characteristic of other water strider genera (e.g., Aquarius, Sih and Krupa 1992;Weigensberg and Fairbairn 1994;Lauer 1996), as well as many other taxa (e.g., Magurran and Seghers 1994;CluttonBrock and Parker 1995;Rehfeldt 1996;Clutton-Brock and Langley 1997;Byrne and Roberts 2000;Crean et al 2000;Galimberti et al 2000;Shine et al 2000), and may similarly constrain mating-system evolution to a relatively small number of trajectories. Only comparative studies of clades, for which experimental studies have elucidated the dynamics of the conflict over mating, can address this proposition.…”

A mixed model of the evolution of polygyny and sexual size dimorphism in mammals

“…In mammals, male coercion has been described as promoting female group formation. In southern elephant seals Mirounga leonina, Galimberti et al (2000) found that females showed a clear preference for larger harems that guaranteed a reduced harassment risk. Red deer Cervus elaphus in Doñana National Park (Spain) distribute themselves in accordance with food dispersion (Carranza & Valencia 1999).…”

Population status, trends and a re‐examination of the hypotheses explaining the recent declines of the southern elephant seal Mirounga leonina

“…It is during these periods ashore that elephant seals are potentially vulnerable to disturbance. Human disturbance may affect a population by: (i) disrupting suckling and the transfer of resources between mother and offspring resulting in lighter weaning mass (Bryden, 1968) and increased mortality (McMahon, Burton & Bester, 2000); (ii) males trampling pups during charges at human intruders (Galimberti, Boitani & Marzetti, 2000b); and (iii) increasing the occurrence of mother–pup separations (Galimberti, Boitani & Marzetti, 2000a). However, no evidence exists for behavioural, physiological or morphometric differences between disturbed and undisturbed seals (Engelhard et al ., 2001, 2002a,b).…”